found that the Tee where the two 12 mm (about 1/2") copper cooling lines meet before going to the salt water heat exchanger was partly plugged by a plastic orifice that is in the line form the turbocharger. It had moved dowstream a few inches and partially blocked circulation.

You do not have a turbocharger, so have perhaps only one line.

Another cause of overheating that we had, and solved, was in the small vent line coming off the top of the thermostat, going forward. It loops back to the fresh water reservoir. If you pull the line off the hose fitting, you will see that it has a very small internal diameter. This is intended by Volvo to allow only a small flow to criculate up to the tank and subsequently back down to the engine. We found that this line would plug with rust (fitting is steel, not brass as it should be) . If plugged, or nearly so, the engine would overheat. I run in small drill (about 3/32") through it every Spring. Doing it by hand, with the drill in a vice grip is all that it needed.